PT07Z  Longest path in a tree
You are given an unweighted, undirected tree. Write a program to output the length of the longest path (from one node to another) in that tree. The length of a path in this case is number of edges we traverse from source to destination.
Input
The first line of the input file contains one integer N  number of nodes in the tree (0 < N <= 10000). Next N1 lines contain N1 edges of that tree  Each line contains a pair (u, v) means there is an edge between node u and node v (1 <= u, v <= N).
Output
Print the length of the longest path on one line.
Example
Input: 3 1 2 2 3 Output: 2
hide comments
anuraag19:
20170802 18:51:15
does anybody know why i am getting runtime error?


karthik_vg:
20170718 13:55:21
dfs + memorization ;) 

sagnik_66:
20170705 10:48:57
Solved using single DFS, this helped : https://cptalks.quora.com/DiameterofaTree 

phben:
20170704 03:24:22
@prashant2018 How to see the test cases? Aren't they hidden? 

ashwani0605:
20170621 06:52:03
Some of the answer in SPOJ toolkit are wrong, so verify on your own 

sandeep_4141:
20170614 10:27:13
dfs 

rahul_nitdgp:
20170606 09:02:40
Only one DFS! 

Anirban Acharya:
20170605 07:56:21
how do you get the root node in these kind of problems on Spoj? For this problem I considered the first node as the root node although any node can be considered as the root for finding the deepest node, but I am asking in general. 

swas99:
20170520 10:48:15
Weak testcases.


Rajat Gautam:
20170518 23:09:07
@prashant2018 Use first bfs to find farthest node. and second bfs starting from this node to find longest path. 
Added by:  ThanhVy Hua 
Date:  20070328 
Time limit:  0.5s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ERL JSRHINO NODEJS PERL6 VB.NET 
Resource:  Coauthor Amber 